Optical encoder

Abstract

An optical encoder comprising a light-receiving part having photodiodes equal in number to the common multiplier of a number of slits facing the light-receiving part and a number of movement information signals. Output terminals of the photodiodes are connected so that the movement information signals are respectively obtained by adding output signals of the plurality of photodiodes out of the photodiodes equal in number to the common multiplier. The twelve photodiodes are balancedly arranged corresponding to three slits and a light-receiving area of each photodiode is made smaller by subdiving each photodiode. The optical encoder suppress difference, distortion and variance of the movement information signals or the like obtained from the light-receiving part with the result that accurate movement information is obtained.

1. An optical encoder which comprises
 a moving body wherein light transmission areas and non-light transmission areas are alternately formed along a moving direction, a light-emitting part for emitting lights toward the moving body, and a light-receiving part for receiving lights emitted from the light-emitting part and transmitted through the light transmission areas and outputting a plurality of independent movement information signals which represent the movement information of the moving body, wherein 
 the light-receiving part which is arranged so as to face a plurality of the light transmission areas, outputs a plurality of the independent movement information signals and comprises photodiodes equal in number to a common multiplier of a number of the light transmission areas facing the light-receiving part and a number of the independent movement information signals; 
 wherein the photodiodes include at least a first group of photodiodes and a second group of photodiodes, the photodiodes in the first and second groups being disposed for a plurality of the light transmission areas of the moving body, and wherein output terminals of the first group of photodiodes are connected so that a first of the plurality of movement information signals is obtained by adding output signals of the plurality of photodiodes in the first group, and wherein output terminals of the second group of photodiodes are connected so that a second of the plurality of movement information signals is obtained by adding output signals of the plurality of photodiodes in the second group; 
 a number of the light transmission areas facing each of the light-receiving parts is three, a number of the independent movement information signals is four, and the light-receiving part comprises 12 photodiodes; 
 when the moving direction of the moving body is considered as a longitudinal direction and an arrangement pitch in the light transmission area is considered as one pitch, the 12 photodiodes are arranged along the longitudinal direction, having a length equal to one-sixth of the pitch respectively; 
 the light-receiving part comprises three photodiode groups, each of which is composed of the four photodiodes, distance between each of the photodiodes in each of the photodiode groups is 1/12 of the pitch, in two adjacent photodiode groups, a photodiode in one photodiode group closest to the other photodiode group and a photodiode in the other photodiode group closet to the one photodiode group are adjoined at a pitch 5/12 of the pitch; and 
 four photodiodes in the photodiode groups respectively output output signals corresponding to four independent different movement information signals, and output one movement information signal by adding output signals of the three photodiodes corresponding to one movement information signal out of four movement information signals outputted from the three photodiode groups. 
 
   
   
     2. The optical encoder as set forth in  claim 1 , wherein a size of the light transmission area of the moving body in a widthwise direction orthogonal to the moving direction and a size of at least one of the photodiodes in the widthwise direction are made equal. 
   
   
     3. The optical encoder as set forth in  claim 1 , wherein
 the moving body is of disk shape wherein light transmission areas of sectorial shape and non-light transmission areas of sectorial shape are circumferentially and alternately formed, and the moving direction is circumferential; 
 a profile of the photodiodes provided for the light-receiving part is made sectorial shape so as to be matched with the light transmission areas of sectorial shape. 
 
   
   
     4. The optical encoder as set forth in  claim 1 , wherein
 additional photodiodes for detecting information other than movement information of the moving body are arranged between the photodiodes provided for the light-receiving part. 
 
   
   
     5. The optical encoder as set forth in  claim 4 , wherein
 the additional photodiodes for detecting information other than movement information of the moving body are arranged between the photodiodes provided for the light-receiving part, and movement information is obtained by adding output signals of the additional photodiodes to output signals outputted from the photodiodes provided for the light-receiving part. 
 
   
   
     6. The optical encoder as set forth in  claim 1 , wherein
 a plurality of photodiodes provided for the light-receiving part are formed on a semiconductor chip; and 
 cross under resistors under wiring for electrically connecting the plurality of the photodiodes are provided which are intersected with the wiring, and the cross under resistors are made by impurity diffusion in the semiconductor chip. 
 
   
   
     7. The optical encoder of  claim 1 , wherein the encoder is provided in a printer and/or copier apparatus. 
   
   
     8. An optical encoder which comprises
 a moving body wherein light transmission areas and non-light transmission areas are alternately formed along a moving direction, a light-emitting part for emitting lights toward the moving body, and a light-receiving part for receiving lights emitted from the light-emitting part and transmitted through the light transmission areas and outputting movement information signals which represent the movement information of the moving body, wherein 
 the light-receiving part which is arranged so as to face a plurality of the light transmission areas, outputs a plurality of the independent movement information signals and comprises photodiodes equal in number to a common multiplier of a number of the light transmission areas facing the light-receiving part and a number of the independent movement information signals; 
 output terminals of a plurality of the photodiodes are connected so that the plurality of the movement information signals are respectively obtained by adding output signals of the plurality of photodiodes out of the photodiodes equal in number to the common multiplier; 
 a plurality of the light-receiving parts having the photodiodes equal in number to the common multiplier; 
 a number of the light transmission areas facing each of the light-receiving parts is three, a number of the independent movement information signals is four, and each of the light-receiving parts comprises 12 photodiodes; 
 when the moving direction of the moving body is considered as a longitudinal direction and an arrangement pitch in the light transmission area is considered as one pitch, the 12 photodiodes are arranged along the longitudinal direction, having a length equal to one-sixth of the pitch respectively; each of the light-receiving parts comprises three photodiode groups, each of which is composed of the four photodiodes, distance between each of the photodiodes in each of the photodiode groups is 1/12 of the pitch, in two adjacent photodiode groups, a photodiode in one photodiode group closest to the other photodiode group and a photodiode in the other photodiode group closet to the one photodiode group are adjoined at a pitch 5/12 of the pitch; and 
 four photodiodes in each of the photodiode groups respectively output output signals corresponding to four independent different movement information signals, and output one movement information signal by adding output signals of the three photodiodes corresponding to one movement information signal out of four movement information signals outputted from the three photodiode groups. 
 
   
   
     9. The optical encoder as set forth in  claim 8 , wherein
 four photodiodes of the three photodiode groups provided for each of the light-receiving parts comprises a first photodiode for outputting an output signal corresponding to a first movement information signal, a second photodiode for outputting an output signal corresponding to a second movement information signal, a third photodiode for outputting an output signal corresponding to a third movement information signal and a fourth photodiode for outputting an output signal corresponding to a fourth movement information signal; and 
 in each of the three photodiode groups in one light-receiving part out of two adjacent light-receiving parts, the first photodiode, the second photodiode, the third photodiode and the fourth photodiode are arranged along the moving direction in order, and in each of the three photodiode groups of the other light-receiving part out of two adjacent light-receiving parts, the third photodiode, the fourth photodiode, the first photodiode and the second photodiode are arranged along the moving direction in order. 
 
   
   
     10. An optical encoder which comprises
 a moving body wherein light transmission areas and non-light transmission areas are alternately formed along a moving direction, a light-emitting part for emitting lights toward the moving body, and a light-receiving part for receiving lights emitted from the light-emitting part and transmitted through the light transmission areas and outputting movement information signals which represent the movement information of the moving body, wherein 
 the light-receiving part which is arranged so as to face a plurality of the light transmission areas, outputs a plurality of the independent movement information signals and comprises photodiodes equal in number to a common multiplier of a number of the light transmission areas facing the light-receiving part and a number of the independent movement information signals; 
 output terminals of a plurality of the photodiodes are connected so that the plurality of the movement information signals are respectively obtained by adding output signals of the plurality of photodiodes out of the photodiodes equal in number to the common multiplier; 
 a number of the light transmission areas facing the light-receiving part is three, a number of the independent movement information signals is four, and the light-receiving part comprises 24 photodiodes; 
 when the moving direction of the moving body is considered as a longitudinal direction and an arrangement pitch in the light transmission area is considered as one pitch, the 24 photodiodes are arranged along the longitudinal direction, having a length equal to 1/12 of the pitch respectively; 
 the light-receiving part comprises eight photodiode groups each of which is composed of the three photodiodes, and the three photodiodes in each of the photodiode groups arranged at a pitch 1/12 of the pitch; 
 the eight photodiode groups is composed of the first to the eighth photodiode groups arranged along the moving direction in order; 
 a pitch between the first photodiode group and the second photodiode group, a pitch between the third photodiode group and the fourth photodiode group, a pitch between the fifth photodiode group and the sixth photodiode group and a pitch between the seventh photodiode group and the eighth photodiode group are 1/12 of the pitch; 
 a pitch between the second photodiode group and the third photodiode group, a pitch between the fourth photodiode group and the fifth photodiode group, and a pitch between the sixth photodiode group and the seventh photodiode group are one-sixth of the pitch; and 
 three photodiodes in each of the photodiode groups respectively output output signals corresponding to different movement information signals from one another, and output one movement information signal by adding output signals of six photodiodes corresponding to one movement information signal out of four movement information signals outputted from the eight photodiode groups. 
 
   
   
     11. An optical encoder which comprises
 a moving body wherein light transmission areas and non-light transmission areas are alternately formed along a moving direction, a light-emitting part for emitting lights toward the moving body, and a light-receiving part for receiving lights emitted from the light-emitting part and transmitted through the light transmission areas and outputting movement information signals which represent the movement information of the moving body, wherein 
 the light-receiving part which is arranged so as to face a plurality of the light transmission areas, outputs a plurality of the independent movement information signals and comprises photodiodes equal in number to a common multiplier of a number of the light transmission areas facing the light-receiving part and a number of the independent movement information signals; 
 output terminals of a plurality of the photodiodes are connected so that the plurality of the movement information signals are respectively obtained by adding output signals of the plurality of photodiodes out of the photodiodes equal in number to the common multiplier; 
 a number of the light transmission areas facing the light-receiving part is two, a number of the independent movement information signals is four, and the light-receiving part comprises eight photodiodes; 
 when the moving direction of the moving body is considered as a longitudinal direction and an arrangement pitch in the light transmission area is considered as one pitch, the eight photodiodes are arranged along the longitudinal direction, having a length equal to a quarter of the pitch respectively; 
 the light-receiving part comprises two photodiode groups each of which is composed of the four photodiodes, and the four photodiodes in each of the photodiode groups arranged at a ¼ of the pitch; 
 in two adjacent photodiode groups, a photodiode in one photodiode group closest to the other photodiode group and a photodiode in the other photodiode group closet to the one photodiode group are adjoined at a half of the pitch; 
 four photodiodes in each of the photodiode groups respectively output output signals corresponding to four independent different movement information signals, and output one movement information signal by adding output signals of two photodiodes corresponding to one movement information signal out of four movement information signals outputted from the two photodiode groups. 
 
   
   
     12. The optical encoder as set forth in  claim 11 , comprising a plurality of the light-receiving parts, wherein
 four photodiodes of the two photodiode groups provided for each of the light-receiving parts are composed of a first photodiode for outputting an output signal corresponding to a first movement information signal, a second photodiode for outputting an output signal corresponding to a second movement information signal, a third photodiode for outputting an output signal corresponding to a third movement information signal and a fourth photodiode for outputting an output signal corresponding to a fourth movement information signal; and 
 in each of the two photodiode groups of one light-receiving part out of two adjacent light-receiving parts, the first photodiode, the second photodiode, the third photodiode and the fourth photodiode are arranged along the moving direction in order, and in each of the two photodiode groups of the other light-receiving part out of two adjacent light-receiving parts, the third photodiode, the fourth photodiode, the first photodiode and the second photodiode are arranged along the moving direction in order.